1. Field of the Invention
The invention relates to a clamping folder for sheets, and in particular for unperforated written, typed or printed matter, with two folder covers interconnected along a back or spine and a cross-sectionally, approximately U-shaped clip, which is displaceable at right angles to the back axis and is undetachably secured to the folder.
2. Prior Art
A fastener of this type is known, in which the rear folder cover is curved twice by in each case 90.degree. for forming a back or spine. The narrow strip formed as a result of this on the front side is again bent over, so that the bent over part comes to rest between the strip and the rear wall. The free edge is then again folded back forwards, so that a fold is obtained, behind which is fixed the bent over leading edge (U.S. Pat. No. 3099269). The total of four bending operations of the rigid PVC foil represents considerable production effort and leads to a very high production price.
The object of the present invention is to provide a fastener, which has a simpler construction and which is therefore less expensive to manufacture. According to the invention this object is achieved in that the clip is constructed for engagement on an edge directed away from the back of the folder. This edge can be positioned in the vicinity of the back or at a limited distance in front of the same. There is no longer any need for the front leg of the clip to engage in a slot and can instead be visibly arranged on the front side of the front folder cover. The displaceability of the clip in one direction is limited by the back of the folder engaging with the inside of the clip web. In the reverse direction the displaceability is limited by the clip engaging against said edge. In order that the clip can engage on said edge, it can have a barb-like profile. According to a further development the edge is formed by the border of a cut or slot. If the latter is positioned in the immediate vicinity of the back of the folder, it opens automatically as a result of the tension of the material in the back region.
The edge against which the clip engages can also be formed by a forwardly bulged out bead, which can e.g. be produced by deep drawing.
According to a further development, the front folder cover can be formed by a narrow strip connected to the rear folder cover and a translucent or transparent plastic sheet is articulated by means of a film hinge to the border thereof. The fitting of such a film hinge, which can be very easily produced at the time of welding a plastic sheet, ensures that even in the case of a sudden, jerky wide opening of the folder there is no displacement of the clip, so that the fastened written matter remains secured. This also permits the turning of the pages.
According to a further development, the front strip and/or the rear cover is constructed in double-walled manner in the area adjacent to the back of the folder. The double wall can e.g. be produced in that in the vicinity of the back a strip forming the latter can be welded to the rear folder cover and optionally part of the front folder cover. This strip can be made from a softer material than the rear folder cover, which is preferably made from rigid PVC. As a result of the double wall, it is relatively easily possible to produce slits or cuts, which can be used for fixing the clip.
The edge against which the clip engages can be advantageously formed by the border of a punched portion, whose width roughly corresponds to the displacement path and whose length approximately corresponds to the length of the front leg of the clip. The free edge of the front leg of the clip can be located in said punched portion. This ensures that the clip is laterally guided during displacement, so that the user is assisted in the handling of the folder.
According to a further development the contact edge for the clip is positioned on the rear side of the folder, i.e. in the vicinity of the rear folder cover. This is particularly advantageous if the folder is to be used for a thicker stack of written matter, e.g. 3 mm or more thick. There is then no need to provide a barb-like profile from the inside of the front leg, so that the available opening angle is significantly increased. It is naturally also appropriate and possible to construct a flat engagement or contact rib on the inner edge of the front leg, which leads to a reinforcement of the fixing pressure of the clip. This e.g. 0.2 mm thick rib is, however, so small that it does not impair the opening angle. For guiding or fixing the clip on its rear leg, it is possible to provide it there with at least one tongue or the like engaging in an opening. It is particularly advantageously to provide two uniformly distributed tongues. The openings in which said tongues engage can e.g. have a pocket-like construction, so that the tongues are laterally inserted into the same. It is also possible for the tongues to be in the extension of the clip and to engage in in each case one slot at right angles to the back. The attachments are guided in the space between the two walls by the slot, which is now constructed in the outer wall of the double wall part. Various possibilities can be provided for the insertion of the clip, e.g. slots therein, which permit a springing together of the attachments or the like.
It is naturally also possible to guide both the front and rear of the clip and to engage same against contact surfaces.
According to a further development, the front leg of the clip can engage in a slot provided in the front folder cover and the edge of the clip is fixed behind the edge of the slot facing the folder back. As a result of these inventively proposed measures, it is possible to effect only a single folding operation for producing such a clamping folder, namely a 180.degree. fold for forming the folder back. The slot which has a certain distance from the back simultaneously serves to prevent the complete pulling out of the clip. However, it is no longer necessary to carry out a multiple turning or wrapping over of the strip on the edge of the folder back, in order to form an abutment for the clip.
According to a further development, in the vicinity of the slot on the side of the front cover facing the rear cover is fixed an insert in such a way that the front leg of the clip engages on the front of the insert. This ensures that the clip does not engage directly onto the documentation to be secured, which is located between the insert of the rear folder cover.
According to a further development, the front folder cover is formed by a strip optionally connected in one piece of the rear folder cover and a sheet fixed to its inside extending between the strip and the rear folder cover approximately up to the edge of the slit facing the folder back. This leads to the formation of a folder which, despite a considerably simplified manufacture, corresponds in appearance to the existing folders of this type. The strip can be made roughly as wide as the front leg of the clip.
Naturally the strip and the rear folder cover can be formed from separate parts, which are connected directly or with a back. In the case of production from plastic, said parts can be interconnected by a welding process, which makes it possible to produce several weld seams.
According to a further development of the invention, in the vicinity of the slot, the front sheet is only connected to the strip in the vicinity of its edge remote from the folder back. This means that a portion of the front sheet projecting in the direction of the folder back forms the insert on which the clip engages, so that the clip is not in contact with the paper to be secured.
According to the invention, the folder can be made from plastic, which has the necessary strength. It is particularly favorable to make the rear folder cover and optionally the strip, from PVC, particularly rigid PVC, whilst the front sheet is advantageously made from a translucent or at least transparent plastic. This front sheet can also have a reduced rigidity compared with the rear cover.
The hitherto used spring steel clips must be hardened, cleaned and painted. This is not always particularly easy in view of the relatively complicated shape, so that the results are not always satisfactory. Thus, e.g. paint dust can be deposited on the clips and there is also a corrosion risk. Therefore the present invention proposes making the clip from plastic. This also has the advantage that for preventing the dropping out of the clip there is no longer a need, as is the case with spring steel clips, to bend over the leading edge of the front leg and in fact a small undercut, e.g. in the form of an edge is adequate.